Background: Little is known about whether cannabis and tobacco use are indicators of suicide and overdose risk. This longitudinal study aimed to examine associations between cannabis and tobacco use with risks of suicide attempt/death and overdose death over a 2-year follow-up in a large cohort of Veterans prescribed opioids.

Methods: We analyzed a national cohort of 923,291 Veterans receiving opioid analgesics in Veterans Health Administration clinics during 2014-2019. Cannabis and tobacco use were assessed at cohort entry. Outcomes (suicide attempts, suicide death, overdose death) were obtained at follow-up through 2021. We used cause-specific hazard models to examine associations between cannabis and tobacco use with each outcome adjusting for well-established risk factors for suicide/overdose (e.g., substance use disorders, mental health, socio-demographics).

Results: At baseline, 5.4% of the cohort used cannabis, and 39.4% used tobacco. At the end of follow-up (median follow-up time was 6.7-6.8 years), 2.2% of the sample had attempted suicide, 0.4% had died by suicide, and 0.5% had died by overdose. In adjusted models, cannabis use was associated with a higher risk of suicide attempt (hazard ratio [HR] 1.11, 95%CI: 1.06-1.15). Current use of tobacco (versus never use) was associated with higher risk of suicide attempts (HR 1.18, 95%CI: 1.13-1.22), suicide deaths (HR 1.19, 95%CI: 1.07-1.32), and overdose deaths (HR 1.67, 95%CI: 1.51-1.83).

Conclusions: Findings indicated cannabis and tobacco use were associated with suicide attempts/deaths and overdose deaths among Veterans prescribed opioid analgesics, underscoring a need for monitoring patients who use tobacco and cannabis in this population.